The technology relates to a vehicle power source that may be mounted on a vehicle.
As a vehicle power source that may be mounted on a vehicle, a power source has been developed that includes a plurality of power storages. As such power storages that constitute the power source, lead batteries, lithium ion batteries, and other batteries have been used (refer to Japanese Unexamined Patent Application Publication (JP-A) No. 2014-36557). In a power source described in JP-A No. 2014-36557, regenerative electric power may be recovered in vehicle deceleration; and the regenerative electric power thus recovered may be charged not only in a lead battery but also in a lithium ion battery. This makes it possible to regenerate much electric power in the deceleration of a vehicle, leading to enhancement in energy efficiency of the vehicle.
However, in the power source described in JP-A No. 2014-36557, a terminal voltage of the lithium ion battery is set lower than a terminal voltage of a lead battery. Accordingly, in order to positively allow for charge and discharge of the lithium ion battery described in JP-A No. 2014-36557, it has been desirable to provide a dedicated discharge circuit on the lithium ion battery side, or to incorporate a converter in the power source. Moreover, at the time of restart, it has been desirable to couple an instantaneous voltage drop protection load to the dedicated discharge circuit, allowing for protection of the instantaneous voltage drop protection load. Such complication of a control method and a circuit structure of the power source has been one factor that may incur increasing costs of a vehicle power source.